Three people arrested in connection with an incident on Collingwood Road in Billingham on the evening of Saturday have now been released on conditional bail in connection with the suspicious items found.
One of the three arrested has been remanded to appear at court in connection with an assault, unrelated to this incident.
Police enquiries are continuing, with officers carrying out further investigations at an address in Howard Walk in Billingham today.
A fourth person has been arrested in relation to the investigation and is currently in police custody where he will be questioned by officers.
Acting Detective Chief Inspector Barnes said: “I would like to reassure the public that it is usual practice to carry out a thorough investigation in circumstances such as this.
“Whilst the presence of the Explosive Ordnance Disposal (EOD) experts may cause some concern for those living in the area, please don’t be alarmed whilst these enquiries are carried out. A police cordon will be in place and officers will remain in the area throughout the course of the investigation.”
Anyone with information should contact us on 101, quoting reference number 186330.